Alfredo Dubra - US grants

? DESCRIPTION (provided by applicant): Early detection of eye disease is critical for preventing vision loss that affects more than 38 million Americans. Current diagnostic tools often reveal retinal changes only after vision loss has already occurred. Tests of visual function are limited by their subjectivity, and by the pooling of signals from tens to thousands of retinal cells. Tests of retinal structure are limited by the substantial anatomical variation among individuals, which makes early disease detection impossible without baseline measurements. In most cases structural tests can therefore detect only macroscopic changes that follow major cell death. These limitations could be overcome by a non-invasive method to detect chemical changes that precede cell death. For this purpose, we will develop two novel technologies, adaptive longitudinal chromatic aberration (LCA) correction and axially- resolved hyperspectral retinal imaging. These will be demonstrated in combination with ophthalmic adaptive optics, to characterize the spectra of idiopathic epiretinal membranes, with or without associated retinal traction or macular hole, as well as age-related macular degeneration and central serous retinopathy.

? DESCRIPTION (provided by applicant): Strategies for treating degenerative retinal diseases are evolving at a rapid pace; however there exist major gaps impeding progress towards the ultimate audacious goal of regenerating neurons in the eye to restore sight. Technologies for monitoring the presence and health of individual photoreceptors and ganglion cells in living animal and human retinae are desperately needed. These tools would provide critical insight into the pathogenesis of a number of retinal and neuro-degenerative diseases; such insight is a requisite first step to developing the appropriate therapeutic approaches for a given patient/disease. Furthermore, improved visualization of cellular structure and function in patients with retinal degenerative diseases will permit scientists and clinicians to more precisely target and monitor the outcome of their therapeutic interventions. We have assembled a multidisciplinary research team uniquely equipped to address this major technological need. Drawing on our extensive experience in developing adaptive optics and retinal imaging tools, we propose to develop and disseminate four complementary platform/enabling technologies. We will leverage our existing collaborative relationships among all five participating sites, synergisic expertise, and access to extensive animal models along with an unrivaled patient population for testing these technologies. The specific technologies we propose to develop are: 1) Real-time retinal motion compensation, allowing retinal cellular-resolution imaging even in cases of extreme involuntary eye motion, like nystagmus; 2) Adaptive longitudinal chromatic aberration correction, allowing multi-wavelength, cellular-resolution retinal imaging; 3) Super- resolution line scanning ophthalmoscopy, to non-invasively image previously inaccessible cells and provide the largest image resolution improvement (> 50%) since the original demonstration of ophthalmic adaptive optics; and 4) High-throughput, opto-physiological method for assessing photoreceptor function with cellular resolution, providing a sensitive biomarker for assessing the function of regenerated/restored cells. A major strength of this application is that through our collaborative network we will validate the utility of these new technologies using regenerative therapies in both pre-clinical and clinical settings. This work will have a significant positive impact by enabling diagnosis of retinal disease and monitoring of retinal structure and function with unprecedented sensitivity and resolution. Finally, the focus of the proposed technologies will be photoreceptor and retinal ganglion cell imaging to explicitly advance the audacious goal, but they will not be limited to assessing any one therapeutic approach or cell type. Rather they will be generalizable and broadly applicable to all retinal cell types, retinal diseases, and therapeutic strategies.

PROJECT SUMMARY There is an important unmet need in glaucoma to develop next-generation functional imaging modalities. The advent of high resolution retinal imaging technologies, specifically, optical coherence tomography and adaptive optics scanning laser ophthalmoscopy, has enabled evaluation of retinal anatomical features at a cellular level in living human eyes. However, assessment of anatomy only provides limited information about the health and function of the retinal tissue. There remains a pressing need for molecular and metabolic endpoints in evaluating glaucoma, where structural changes may take many years to appear, often associated with significant vision loss. Currently available techniques for assessment of retinal blood flow, oxygen saturation, and mitochondrial function in humans have limited depth discrimination and require separate instruments, hampering accurate and comprehensive quantification of retinal ganglion cell physiology. Thus, we propose to develop and validate an innovative depth-resolved retinal metabolic imaging system, scanning protocols and analysis algorithms to non-invasively, quantitatively and simultaneously assess retinal oxygen and mitochondrial metabolism in glaucoma, and in response to candidate neuroprotective or regenerative therapies, both in animal models and in human subjects. We will perform pilot studies to demonstrate and validate the technology's capability to provide metabolic measures relevant to vision restorative therapies in animals and humans. The availability of novel retinal metabolic measures will for the first time introduce a physiologically-based outcome measure for disease characterization and also for candidate therapies relevant to regenerative ophthalmology and vision restoration. In addition, the proposed research will have a significant impact on advancing: 1) knowledge of retinal metabolic dysfunction in animal models of human glaucoma and other optic neuropathies, 2) translation of candidate regenerative therapies that improve retinal metabolic function in pre-clinical studies, and 3) clinical assessment and evaluation of available and emerging therapies for restoring vision in glaucoma, as well as in other degenerative retina/optic nerve diseases.

PROJECT SUMMARY Adaptive optics (AO) ophthalmoscopy allows non-invasive visualization of microscopic retinal structures by correcting the optical blur that is unique to each eye, potentially enabling improving the understanding and management of eye disease. Lack of standardization, however, has hindered the adoption of this technology in the multi-center studies that are the gold standard for testing novel treatments. The overarching goal of this project is to improve rigor and reproducibility in AO ophthalmoscopy, in order to materialize its potential through three specific aims: Aim 1. To develop, build and distribute calibrated model eyes that allow precise compensation of image distortions and scaling errors caused by the optics of AO ophthalmoscopes. These model eyes will be designed to be reproducible by others and have similar optical properties to those of an average human eye. Aim 2. To develop imaging protocols and algorithms that use whole-eye optical biometry to allow precise compensation of image distortions and scaling errors caused by the unique optics of each eye. Aim 3. To collect an open normative dataset of photoreceptor mosaic images in subjects free of eye disease, and to use it to test two hypotheses. First, that rod photoreceptors are lost to aging at a rate of ~1% per year in the central portion of the retina that is affected in various leading blinding conditions, such as age-related macular degeneration. Second, that rod photoreceptor spacing increases with cell loss, offsetting the decline in density, and thus can be used for detecting early signs of disease. The image scaling and distortion correction methods from Aims 1 & 2 will improve our ability to perform these tests. The deliverables of this project will incorporate feedback and testing by the AO retinal imaging community. At this project?s conclusion, users of AO ophthalmoscopes will receive software and calibrated model eyes for precise image scaling and correction distortion, as well as the most anatomically truthful and accurately scaled photoreceptor normative dataset. The proposed practices will facilitate the development of retinal imaging biomarkers that improve early diagnosis and management of eye disease, as well as testing of novel therapies.

PROJECT SUMMARY The optics of the eye suffer from imperfections (wavefront aberrations) that blur retinal images. This blur limits our ability to diagnose eye disease before irreversible damage and vision loss take place. Adaptive optics (AO) ophthalmoscopy can correct for this blur, which is unique to each eye and retinal location. Current AO ophthalmoscopes can only capture images of very small retinal areas because they cannot correct for the variation of the wavefront aberrations across the retina. This limitation impedes the use of this technology for detecting early signs of disease, which in turn, enable the early treatment that would mitigate irreversible vision loss. Here we propose to first measure how wavefront aberrations change across the retina in a human subject population to improve the design and operation of all future AO ophthalmoscopes. We also propose two novel methods for measuring and correcting wavefront aberrations that vary across the retina to increase the field of view of these instruments. First, we propose to measure aberrations sequentially at various points in the field of view and then deliver appropriate sequential wavefront corrections at each retinal location. This low-cost, low complexity approach could be used to double the retinal coverage of current AO scanning ophthalmoscopes. The second approach uses two wavefront correctors, the optimal axial positions of which will be determined by using the data on wavefront aberration changes with retinal location and wavelength across the population. This more complex approach aims to at least quadruple retinal coverage. The resulting increase in the field of view will be a major step towards translating AO ophthalmoscopy into a practical clinical tool for improving the diagnosis and treatment of eye diseases.

PROJECT SUMMARY Adaptive optics (AO) scanning ophthalmoscopy allows non-invasive visualization of microscopic retinal structures by correcting the optical blur that is unique to each eye. In these instruments, however, image distortion due to involuntary fixational eye movement is a barrier to improving the understanding, early diagnosing, and management of eye disease. We propose to develop high-bandwidth eye motion stabilization technology and image registration software to mitigate this distortion even in subjects with the most extreme forms of involuntary eye motion, including nystagmus. This will be achieved by using a high frame rate pupil tracker that measures the eye?s orientation and by steering galvanometric optical scanners to simultaneously stabilize the view of the pupil and the retina as seen by AO scanning ophthalmoscopes with sub-millisecond total latency. Our goal here is to develop low-cost, low-complexity, and high-bandwidth retinal imaging stabilization instrumentation that can be used to upgrade both AO and non-AO ophthalmoscopes, using control algorithms that incorporate eye motion prediction, electronic and mechanical latency. Finally, we will also develop image registration software for scanning ophthalmoscopes that uses the high frame rate pupil tracking to improve accuracy and reduce failure rate, as well as automate the identification of and un-distort reference frames. The proposed technology will be applicable to all scanning ophthalmoscopes, irrespective of imaging modality.